A Walmart gun display prodding customers to "Own the school year like a hero," was a prank, the company confirmed Saturday.

Walmart spokesman Charles Crowson told USA TODAY the company is "certain" the incident was a ruse, but offered no other details.

Walmart started its own investigation of the incident Wednesday, after a photo of the display spread across Twitter. The photo showed a glass gun case in a Walmart store with a sign on top reading, "Own the school year like a hero," the store's back-to-school slogan.

The photo drew quick condemnation from people online and the company itself. Over a 24-hour period, the company tweeted out dozens of apologies to individual tweeters, calling the display "terrible," "definitely NOT okay" and a "regrettable situation."